This application addresses broad Challenge Area (04) Clinical Research, specific Challenge Topic 04-HL-104 "Perform secondary analyses of existing data to answer important clinical and preventive medicine research questions." We propose to use existing data from the Veterans Aging Cohort Study (VACS) to examine risk factors for incidence and severity of bacterial pneumonia in HIV infected (HIV+) compared to HIV uninfected (HIV-) patients. VACS is an ongoing multi-site prospective study of 3,413 HIV+ and 3,413 age-, race/ethnicity- and site-matched HIV- patients, enrolled 2001-2002 at 8 US VAMC. We will use the wealth of data that is already available in VACS, and add to this full chart reviews in patients with bacterial pneumonia. We propose the following aims: 1. Determine risk factors for incident and recurrent bacterial pneumonia;2. Determine risk factors for severity of bacterial pneumonia;3. Describe hospital utilization and mortality according to severity of bacterial pneumonia. We will comprehensively examine the relationship between risk factors and processes of care with etiology, severity, and outcomes of pneumonia adjusting for potential confounders. Pneumonia events will be validated by chart review and categorized as incident or recurrent, and as community or hospital acquired. Severity of pneumonia will be described by the pneumonia severity index (PSI) at presentation. As rates of bacterial pneumonia remain elevated among HIV+ patients in the current era of combination antiretroviral therapy (CART), even among those with CD4 cell counts >500, we seek to identify potentially modifiable factors that may provide the basis for future preventive studies. In particular, we are interested in alcohol as a risk factor for incidence and severity of pneumonia, as alcohol use is common in HIV+ populations;is associated with increased risk of pneumonia;immune dysfunction;and acute lung injury. Thus, alcohol use, even at low levels in HIV+ patients, may enhance susceptibility to lung injury related to bacterial infection and predispose to severe disease. These analyses will provide results that have an immediate impact to inform patient care, and will provide a basis for intervention work to decrease risk and improve health care and outcomes from bacterial pneumonia. PUBLIC HEALTH RELEVANCE: This research project seeks to identify risk factors in HIV infected and uninfected individuals that influence the development and severity of bacterial pneumonia, a major source of morbidity and mortality world-wide. In particular, we will investigate the relationship of alcohol use and abuse with bacterial pneumonia, as alcohol may increase the risk for lung injury. These studies can inform patient care and provide a basis for future studies aimed at preventing and improving outcomes from bacterial pneumonia.